The invention relates to an x-ray diagnostic generator for operation with falling load with a function generator which, during an x-ray exposure, generates a rated signal value for the x-ray tube output proceeding according to a falling exponential function, which effects the adjustment of the x-ray tube output via control means.
As a function generator, it is known to employ a capacitor which is charged before the beginning of an exposure to a value which corresponds to the peak value of the x-ray tube output and is discharged via a discharging resistor during an exposure corresponding to the temporal course of the highest allowable x-ray tube output (German OS No. 2,122,138). Thereby, the capacitor represents the rated value generator in a control loop for the x-ray tube output. The actual value of the x-ray tube output is thereby independent of disturbances, for example network voltage fluctuations.
In an x-ray diagnostic generator of this type, it is possible that, for instance because of a faulty working of the control means or of the controlled-gain amplifier, an overload of the x-ray tube ensues because the actual value of the x-ray tube output remains constant during an exposure despite the exponential drop of the rated value signal.